Process for thermal treatment of hydrocarbons



M. B. COOKE Oct. 18, 1933.

PROCESS FOR THERMAL TREATMENT OF HYDROCARBONS Filed July 6, 1936 IINVENTOR Maur/c e B. C'oake Of: ATTORN Y Patented Oct. 18, 193$ UNITED'STATES PROCESS FOR THERMAL TREATMENT OF I HYDROCARBONS Maurice B. Cooke,Plainfleld, N. J.

Application July 6, 1936, Serial No. 89,089 g 6 Claims.

My invention relates to a process for the treatment of petroleumhydrocarbons to produce therefrom primarily lower molecular weighthydrocarbons by thermal decomposition and synthesis of the hydrocarbonsundergoing treatment and, more particularly, so to conduct suchtreatment as to produce not only lower molecular weight gasoline-likehydrocarbons suitable for use as a motor fuel of high anti-knockqualities, but in addition to secure an increased yield of hydrocarbonsof the aromatic series including naphthalene, benzol, xylol and toluol.

When fuel is burned with no excess of air, the temperature of combustionis between 3000 F. and 4000 F.,Such temperatures are too high for theproposed thermal treatment productive oi the desired products andaccordingly this temperature must be brought down considerably in orderto produce-most efliciently the greatest yield of the desired products.

In my co-pending applications Serial No. 598,- 503 filed March 12, 1932,now-Patent No. 2,046,501,

issued July 7, 1936, to Maurice B. Cooke, and

Serial No. 598,504, filed March 12,1932, now Patent No 2,046,502, issuedJuly 1936, to Maurice B. Cooke, I have disclosed a process for thethermal treatment of petroleum hydrocarbons for the productionof lowermolecular weight gasoline-like hydrocarbons by the direct commingling ofhot combustion gases with the hydrocarbons being treated. I have, showntherein that the temperature of from 00 F.

to 4000 F. obtained by the generation of these gases may be lowered to atemperature more favorable for the treatment of the hydrocarbons by'tempering or cooling the gases with steam which may be condensed in apreiractionating condensing. zone with considerable advantages beingobtain-ed in permitting a reduction in the size of fractionating andrecovery equipment over that required where normally incondensible inerttempering gases are employed. In addition, I have shown that thecombustion gases may be tempered in part by passing oil to be heated forvarious ancillary related steps of the process in indirect heat exchangewith the hot gases. In particular, I have disclosed; the indirect heatngof a relatively heavy petroleum oil to prepare it for a toppingoperation; the indirect heating of the topped oil to enable theformation oi. hydrocarbon vapors for subsequent direct thermal treatmentwith the tempered combustion gases; and the'indirect reheating of acooled condensate oi the thermally treated vapors to eflect distillationand permit subsequent fractionating or the distillate vapors forultimate recovery of the desired products.

The character 'of the liquid ultimately produced as a desired productfrom petroleum hydro-- carbons as disclosed in the processes or theforegoing applications, is essentially dependent upon the time,temperature and pressure conditions employed. 1

It is an object of my invention to produce low molecular weighthydrocarbon products including liquid aromatic products such asnaphthalene, benzol, xylol and toluol from heavier petroleumhydrocarbons by the direct thermal treatment of such heavierhydrocarbons with hot combustion gases under closely controlledconditions of time, temperature and pressure.

It is another object of my invention to extract the desired productsfrom the mixture of thermally treated hydrocarbons and combustion gaseswith fraction'ating and separating equipu ment no greater in size thanis normally employed for the extraction of such products from thermallytreated petroleum hydrocarbons not admixed with combustion gases.

It is a iurther object of my invention to effect in the same thermaltreating zone, a secondary or final conversion into desired products, ofsuch hydrocarbons lower boiling than the desired products as arerecovered from the products of the thermal treating operation andrecycled to the treating zone.

It is another object of my invention to coordinate the thermal treatmentof petroleum hydrocarbons occurring when such hydrocarbons are directlycommingled with hot combustion gases, with distillation of the liquidpetroleum hydrocarbons for the production of hydrocarbon vapors to betreated, and the tempering or cooling of the combustion gases to thedesired treating temperature.

- It is a further object of my invention to secure an increased yield ofdesired liquid aromatic and low molecular weight lhydrocarbon productsby close control of the character and quantity of the recycle oilreturned to the primary thermal treating zone for retreatment with freshoil.

Other and further objects of my invention will appear from the followingdescription and the appended claims. I

The accompanying drawing-which forms part of the instant specificationand is to be read in conjunction therewith is a schematic showing inelevation with parts in section of one form of apparatus capable ofcarrying out the process or my invention. g

. addition of a cooler inert gas such as steam and partially by passingthe gases in indirect heat exchange with cooler liquid petroleum hydrocarbons.

- Crude oil is passed in indirect heat exchange with the hot combustiongases whose temperature is thereby lowered while the reduced crude isheated, the heated crude then being subjected to a topping operation inwhich the depth of the out may vary within wide limits. The toppedcrude, together with light and heavy recycle oil, forms the charge to avaporizing coil through which it passes in indirect heat exchange withthe gases, the heated" oil then being flashed into vapors. Preferably,the vaporizing coil is located in the hottest portion of the zonethrough which the combustion gases are being passed. In view of thequantity of oil passing through this coil, it may be necessary to employexternal heating means auxiliary to the combustion gases to secure thedesired vaporization. The vapors resulting are directly commingled in amixing zone with the combustion gases which, on entering this zone, havebeen tempered or cooled to a temperature of from about 1500 F. to about2500" F., the temperature preferably being from about 1800 F. to about2000 F. The mixture of hydrocarbon v'apors and combustion gases, whichfor convenience I shall hereinafter call the reactant, passes through aprimary treating zone of a length suflicient to provide the time elementnecessary to efl'ect decomposition of heavier hydrocarbons of thereactant into lighter hydrocarbons into desired aromatic products. Thereactant is preferably subjected to the action "of the hot combustiongases. in this primary zone for a period 01' from about one second toabout three seconds, depending upon whether the temperature of thesegases is at 2500 F. or a lower temperature of around 1500" F.respectively.

The reactant passes from the primary treating zone into a secondarytreating, or soaking zone, wherein the reactant is cooled to atemperature ,0! from about 1050" Fvto about 1800 F. by the spraying intothe reactant of a cooler recycle oil substantially completelyvaporizableat the re-' sulting temperature, or by indirect heat exchangewith a cooler oil. In this secondary treating zone the recomposition andsynthesis of hydrocarbons proceeds to form not only lower molecularweight gasoline-like hydrocarbons, but, by reason of the lowertemperature, a'substantial quantity of hydrocarbons of the aromaticseries including naphthalene, benzol, toluol and xylol. The time oireaction in this; zone will vary from about one second to about tenseconds, depending upon whether the-temperature o! the re-- actant isabout 1800 F, or 1050" F. respectively.

From the. secondary treating zone, the reactant' passes into a combinedquenching and separating zone wherein a cooler hydrocarbon oil issprayed into the reactant whose temperav ture iszquickly reduced toaround 600 F. to

"'100-F.- -Atthe..same time and as the result of this quenchingoperation, the heavy polymers, tars, gums and fuel oil present arecondensed and are then withdrawn from the quenching zone and theprocess. The uncondensed portion of the reactant is then cooled furtherby passing in, indirect heat exchange with clean water, thus generatingsteam which is utilized for initially tempering the combustion gases,and as process steam for stripping in the main fractionator. The furthercooling of the reactant takes place in a series of separate zones inwhich the heavier hydrocarbons of the reactant are condensed and fromwhich they may be selectively withdrawn. A portion or all of the heavycondensate formed in these separate condensing zones is returned to thequench zone as reflux for end point control and another portion of thisheavy condensate is passed to the main fractionating tower. Theuncondensed lower boiling portion of the reactant which may be, forexample, a 200 F. to 250 F. end point naphtha plus all lighterhydrocarbons and the combustion gases, is further cooled by indirectheat exchange to condense preferablysubstantially all the normallyliquid hydrocarbons. The water resulting from condensation of steam inthe mixtur is withdrawn from the separating zone to which the cooledreactant is passed and the liquid hydrocarbons of the reactant areregeneratively reheated by passing in indirect heat exchange with thereactant and then by passing in indirect heat exchange with the hotcombustion gases, the liquidreactant being raised thereby in adistillation coil to a temperature suflicient to permit vaporization atthe substantially atmospheric'pressure under which the process isconducted. On issuing from this dis-.

main fractionator.

In the main iractionator relatively heavy cracked gas oil is withdrawnas a bottom product, light gas oil'is withdrawn"v as a sidestream, andthe overhead product of the fractionator consists of lower molecularweight gasoline-like hydrocarbons and/or hydrocarbons of the arcmaticseries including naphthalene, benzol, toluol and xylol which are cooled,condensed and removed from the accumulator-separator as the desireddistillate product, The uncondensed portion of the fractionator overheadwhich will include saturated and unsaturated hydrocarbons of theparaflin series such as propane-propylene, butane-butylene,ethane-ethylene, as well as some hydrogen, methane and entrainedgasolinelike hydrocarbons is combined with the uncondensed portion ofthe reactant, compressed,

cooled and the light condensate resulting sepacompression and coolingoperation arepassed to i an absorber wherein they are contacted underpressure with cooled light absorber oil withdrawn as a side stream fromthe main tractionator, the unabsorbed gases particularly the combustiongases and methane being released to. a fuel gas main and the richabsorption 1011 being recycled to the vaporizing coil as part of thechargeto of a valve 34 in the line 29 thus causing the oil to" flowthrough a pipe 35 in which valve 36 is pipe II, and discharged throughpipe I2 into the fuel gas supply tank I3. The fuel gas is dischargedunder pressure as needed from the supply tank |3 through the valved pipe|4 into the mixing chamber l5 wherein it is mixed with air fed through avalved pipe l6 in quantities sumcient to produce complete combustion ofthe gas without excess of oxygen. The combustible mixture formed burnswith surface combustion on the granules of refractory material H to formhot combustion gases in the combustion chamber I6; These hot gases willbe at a temperature of. from 3000 F. to 4000 F..which'is too high forthe eflicient thermal treatment of hydrocarbon vapors in accordance withmy process.

The temperature of these gases may be reduced in part by admixingtherewith cooler steam fed 'into the gases through the valved pipe I9 ata point 20 inthe combustion chamber l3 where complete combustion of thegas fuel air mixture has taken place. The steam thus'supplied will actas an additional heat carrier medium with the combustion gases, and hasthe advantage of being condensible and separable from the combustiongases and hydrocarbon vapors at normal atmospheric conditions oftemperature and pressure. For this reason I am enabled to reduce thequantity of vapor to be passed through the main fractionating tower. Thecombustion gases partially cooled by the steam, if such cooling isdesired at this time, flow into the chamber 2| and across the tubesforming the heating coil 5. The relatively cool oil passing through theheating coil 5 assists in reducing the temperature of the combustion gasand is at the same time heated to a vaporizing temperature preparatoryto fractionation in the fractionating tower 1. Obviously, the heatingeffected in the coil 5 may be supplementedby an external tube still (notshown) and if no topping operation is necessary or if the cooling effectof the coil 5 on the combustion gases is not deemed necessary, this coilmay be dispensed with entirely.

In the fractionating tower I the vapors formed are fractionallyseparated and the overhead products of desired end point flow throughvapor pipe 22, vapor heat exchanger 3 and water cooler 23 intoaccumulator 24 from which reflux is returned through pipe 25 by pump 26to the fractionating tower 1 for end point control of the fractionatoroverhead. Any steam condensed is discharged as water from theaccumulator 24 through the valved pipe 21 and the distillate isdischarged to storage through the valved pipe 26.

The topped crude accumulating in the base of the tower 1 is withdrawntherefrom through a pipe 29 by means of pump 30 and passes through heatexchanger 4, vapor heat exchanger 3!, and

heat'exchanger 32 into .the vaporizing coil feed tank 33. 'All or partof the oil in the pipe 23 may be diverted therefrom by suitablemanipulation opened and through cooler 31'into.a topped oil accumulator36 from which the oil may be withdrawn through pipe 39 by means of apump 40 discharging into the feed pipe 29 connecting with feed tank 33as previously described."

The feed tank 33 contains the oil which is to beheated in a vaporizingcoil and after vaporization thermally treated by direct contact withcombustion gases of proper temperature, and in the case where theinitial charge oil has been subjected to an initial topping operation aspreviously described, consists of this topped oil such as heavy gas oil,and cracked recycle gas oil recovered in the operation of the process aswill be more fully described hereinafter.

The oil to be treated is.withdrawn from the feed tank 33 through thepipe 4| by means 01' the pump 42 which forces the oil through the pipe43, through the valves 44 and 45 in the pipe 43, through the vaporizingheating coil 46in the chamber 2| from which the heated oil istransferred through the pipe 41 into the flash tower 46. The oilcirculating through the coil 46 is heated during transit to a vaporizingtemperatureand at the same time the combustion gases are partiallycooled by indirect heat exchange with the colder oil. In view of therelatively large quantity of oil passing through this heating coil, Imay deem itnecessary to provide additional means for heating the oilsuch as a tube still (not shown) externally of the chamber 2|,

connected into the pipe 43. By such means, I can obtain a very closecontrol of the temperature change of the combustion gases by the coil46. A pipe 43 controlled by a valve 50 connects the pipes 43 and 41 inorder that all or part of the oil from pipe 43 may be passed directlyinto the flash tower 43 as operating conditions with respect totemperature may dictate.

The coil 46 is preferably placed in the chamber 2| in such position asto come in contact with the combustiorigases attheir highesttemperature, although the exact positioning and arrangement of the tubesforming the coil '46 will be governed by the furnace design and by theamount of tempering of the combustion gases con emplated.

In the flash tower 48, the heated oil from pipe 41 is flashed intovapors and unvaporized ,oil, which latter forms a fuel oil and iswithdrawn through the pipe 5|, valve 52, heat exchanger 53 and cooler 54by the pump 55 which discharges 'the fuel oil to storage.

- The hydrocarbon vapors formed in the flash tower 48 dischargetherefrom at substantially atmospheric pressure through the pipe 56 intothe mixing chamber 5'! wherein they are mixed with the combustion gasesissuing from the' chamber 2|.

The combustion gases entering the mixing chamber 51 will have beenreduced in temperature by the steam and indirect heat exchange to atemperature between about 1500 F. to about .2500 F. and preferably to atemperature such that the mixture of hydrocarbon vapors and combustiongases will be at a temperature of from'about 1800 F. to about 2000" F.which I have found is most favorable for the primary thermaldecomposition or cracking of the heavier hydrocarbons of the mixture toproduce lower,

ing zone 51 into the primary treating or cracking zone 58, the time ofpassage of the reactant through which varies from between about onesecond at 2500 F. to about three seconds at 1500 F.

The reactant leaves the primary thermal treating zone 58 after theproper time interval and enters the secondary thermal treating orpolymerizing zone 59 wherein the reactant is cooled to a temperaturebetween about 1050" F. to about the reactant through the secondarytreating zone will vary from about one second at 2000 F., to about fiveseconds at 1400 F., to aboutten seconds at 1200 F. V

The reactant on leaving the secondary treating zone 59 enters aseparator 6| wherein the temperature is quickly lowered to around 600 F.to 700 F. to substantially terminate further reaction by spraying intothe reactant a cooler oil through a suitable quench nozzle 62. The heavypolymers, tars and gums of the nature or fuel oil which are condensed inthe separator 6| are discharged through the valved'pipe 53 into the pipe5i and sent to storage with the fuel oil from flash tower 48.

Theuncendensed portion of. the reactant rises upwardly through aplurality of fractionating trays 84 countercurrent' to downflowingcooler reflux oil. The reactant of desired end point discharges from theseparaior 6i through the pipe 65 into condensing vessel 65.

The condensing vessel 66 is provided with a cooling coil 61 into whichclean cool water is passed by pump 68 through pipe 69 and cooler l0. Thewater is heated in the coil 61 by exchange with the hot reactant and thesteam formed is discharged through the pipe II into the steam supplytank I2 from which tempering steam is withdrawn at will through the pipeI9.

The reactant in the condensing vessel is cooled to an extent sufllcientto condense the heavier hydrocarbons which accumulating as fractionalcondensate in the condensate basins I3, I4 and 15 may be withdrawntherefromthrough the pipes I6, 'I I and 18, respectively, and returnedin suita ble proportions through the pipe I9 to the separator 6| asreflux by suitable manipulation'ot the valves 80, BI and 82.'

The uncondensed portion of the cooled reactant inthe condensing vessel60 will preferably have as its heaviest constituent a hydrocarbondistillate having about a 200 F. to a 250 F. end

point and discharges from the condensing vessel 66 through a pipe 83,through coolers I0, 84 and 85, and through pipe 85 into separator 81.

In the separator 81, the condensate resulting from the cooling of thereactant will preferably consist primarily of hydrocarbons boiling abovethe pentane or C5 hydrocarbons. The water resulting from condensation ofthe tempering steam is withdrawn from the separator 81 I through thevalved pipe 00.

desirable-tor the production of the desired aromatic products. Theuncondensed portion 01 the reactant in the separator 81 will thereforeconsist of a mixture of those saturated and unsaturated hydrocarbonswhich are normally gaseous at normal atmospheric conditions of temperature and pressure and the combustion gases such as hydrogen, nitrogen,carbon dioxide and carbon monoxide. Obviously there will also be in heatexchanger 94, pipe 95, heat exchanger 53' and pipe 96 to thedistillation coil 91 in the chamoer 2i. If desired, the heat exchanger84 may be lay-passed to the pipe 95 through the valved pipe 98 and,likewise, a portion of the condensate in the pipe 93 may be by-passedthrough the valved pipe 99 into the pipe 43 leading to the vaporizingcoil 46 by suitable manipulation of the valves shown. A valved pipe Iconnecting the pipes 95 and 43 permits the by-passing of a portion ofthe condensate issuing from the heat exchanger 94 into the oil flowingthrough the pipe 42 to the vaporizing coil 40.

The reactant condensate flowing through the distillation coil 91 isheated therein to a temperature sufllcient to permit vaporization of theheated oil at low or substantially atmospheric pressure and isdischarged through the transfer pipe IM to the main tractionator I02.

The heavy condensate separated from the reactant in,the condensingchamber 65 may be transferred in whole or in part through the pipe I03controlled by the valve I04 by suitable manipulation of the valves 8|,82 and I04. In thus returning the heavy condensate from the pipe I03 tothe iractionating tower I02, I am enabled to eflect sharp separation ofsuitable recycle stock such as heavy cracked gas oil for recycling tothe vaporizing coil. Steam from the supply tank I2 may be injected intothe tractionator I02 through the pipe I by opening the valve 200.

From the tractionator I02 there is withdrawn a relatively heavy recycleoil such as cracked gas 32, and cooler I08. Aportionot the oil in the.

pipe I06 passes through the pipe I09 controlled by the valve IIO intothe pipe 02 of the separator 0| for use as quench oil. Another portionof the oil in the pipe I00 is passed through the pipe III controlled bythe valve II2 into the spray nozzle 00 from which it is discharged tocontrol the temperature of the reactant in the secondary treating zone50.

The relatively heavy oil withdrawn from the Iractionator I02 through thepipe I06 is most suitable as recycle oil andflthe greater quantity orthis oil passes through the pipe I06 and from thence through the pipeI12 controlled by the valve II4 into the Ieed'itank 33 from which avapor return line I I5 leads to the main fraction ator I02. I havefound; that for most satisfactory operation of my process, the'ratio ofheavy recycle oil to fresh oil in the feed tank 33 should be from aboutone to one, to three to one.

A light gas oil is withdrawn as a sidestream from the fractionator I02through the pipe II6 by means of a pump III and passes through a coolerlit to an absorber II8 for use as cooled lean absorption oil as will bemore fully described hereinafter.

The overhead products of the fractionator I02 are discharged therefromthrough the pipe I20 and pass through the heat exchanger 3| and coolerI2I to the separator I22 from which con densate is returnedthrough pipeI23 by means of pump I24 to the fractionator I02 as reflux for end pointcontrol of the fractionator overhead. Water is withdrawn from theaccumulator I22 through the pipe I25 controlled by the valve I26 and thedistillate, which I shall refer to as heavy distillate to distinguish itfrom the light distillate recovered from the uncondensed gases in the.accumulator I22 and separator 81, is discharged through the pipe I21 bythe pump I23 as the desired aromatic liquid product.

The gases remaining uncondensed in the accumulator I22 will consist ofhydrocarbons both saturated and unsaturated, uncondensible atsubstantiallyatmos'pheric pressure and at the temperature of the coolingwater employed. These gases will contain entrained low molecular weightgasoline-like hydrocarbons and are discharged through the pipe I23adjoining the pipe 89 feeding the suction side of the compressor I30.The mixture of combustion gases and hydrocarbon vapors is compressed anddischarged through pipe I3I and cooler I32 into separator I33 from whichthe light distillate previously referred to is discharged through thepipe I34 controlled by the valve I35 into the pipe I36 through whichflows rich absorption 011 being delivered from the absorber II3 to thepipe II for recycling to the" vaporizing coil l6. V

The uncondensed ,gases in the separator I33 are discharged through thepipe I31 into the absorber I I9 wherein residual hydrocarbons suitablefor recycling to produce the desired aromatics are absorbed in the leanoil fed to the absorber through the pipe H0 and returned with the richoil through the pipe I 36 to the vaporizing coil.

The unabsorbed gases are discharged through the pipe I33 and pressurerelief valve I33'into the fuel gas main I0 from which they may bedischarged to the atmosphere by opening the valve "I40, or picked up bythe compressor 8 by opening the valve I.

It will be observed that I .have accomplished the objects of myinvention and have provided a process for thermal treatment of petroleumhydrocarbons by the direct commingling of such hydrocarbons withcombustion gases under carefully controlled conditions of time andtemperature. I have provided a process by which the conversion andsynthesis :of the hydrocarbons is effected by the thermal treatment ofthe combustion gases so as to produce an increased yield of liquidaromatic products such as naphthalene,

benzol, toluol, and xylol, together with liquid low molecular weightgasoline-like hydrocarbons suitable for use as motor fuel of highanti-knock rating. I have provided a process in which the yield of thedesired liquid aromatic products is increased through the recovery andrecycling of unsaturated hydrocarbons formedin the reactant by' the"thermal treatment. I have also provided a unitary process in which thetemperature of .the combustion gases is controlled by indirect heatexchange with 011 being passed to various stages of the process and bythe admixture with the combustion gases of a cool inert gas such assteam which is readily condensible and may be employed as a heatcarrying medium withoutrequiring an increased size of the fractionatingap- I paratus.

It willbe observed that certain features and sub-combinations are ofutility and may be em-' ployed without reference to other features andsub-combinations. This is contemplated by and is within the scope of myclaims. It is further obvious that various changes may be made indetails within the scope of my claims. This is contemplated by and is,withinthe scope of my claims. It is further obvious that variouschanges may be made in details within the scope of my claims withoutdeparting from the spirit of my invention. It is, therefore, to beunderstood that my invention is not to be limited to the specificdetails shown and described.

Having thus described my invention, what I claim is:

1. A process for thermally treating petroleum hydrocarbons including thesteps of generating combustion gases having a substantially completeabsence of oxygen, cooling the hot gases to a temperature of from about1500 F. to about 2500 F., admixing dry hydrocarbon vapors with thecooled gases to form a reactant at cracking temperature, soaking thereactant at substantially cracking temperature for from about one toabout three seconds to form normally gaseous, unsaturated hydrocarbons,cooling the reactant to a lower and polymerizing temperature of fromabout 1050 F. to about 1800 F., maintaining the reactant at the lowertemperature for from about one to about twelve seconds to polymerizenor,- mally gaseous, unsaturated hydrocarbons to higher molecularweight, aromatic hydrocarbons,

a lower and polymerizing temperature of from about 1200 F. to about 1800F., maintaining the reactant at the lower temperature for from about oneto about twelve seconds to polymerize said normally gaseous, unsaturatedhydrocarbons to higher molecular weight, aromatic hydrocarbons,

quenching the reactant to a temperature below 700 F. to substantiallyterminate further reaction and recovering aromatic hydrocarbons from thequenched reactant.

3. A process for thermally treating petroleum hydrocarbons including thesteps of generating combustion gases having a substantially completeabsence of oxygen, cooling the hot gases to a temperature of from about1500 F. to about 2500 F., admixing dry hydrocarbon vapors with thecooled gases to form a reactant at cracking temperature, soaking thereactant at substantially the cracking temperature for from about one toabout three seconds to form normally gaseous. unsaturated hydrocarbons,cooling the re- "unsaturated hydrocarbons, cooling the reactant to Iactant to a polymerizing temperature of from about 1050" F. to about1800 F., maintaining the reactant at the polymerizing temperature forfrom about one to about twelve seconds to polymerize the normallygaseous, unsaturated hydrocarbons to higher molecular weight aromatichydrocarbons, quenching the reactant to a temperature below 700 F. andcooling the quenched reactant and separating therefrom a lightcondensate comprising mainly normally liquid hydrocarbons of gasolineboiling range and a heavy condensate comprising mainly hydrocarbonsboiling above the gasoline boiling range, fractionating the condensatesto obtain a plurality of successively higher boiling hydrocarbonfractions,

recovering from one 01 said fractions desired aromatic hydrocarbons,vaporizing another of said fractions and admixing the vapors formed withsaid first mentioned cooled gases as dry hydrocarbon vapors.

4. A process for thermally treating petroleum hydrocarbons including thesteps 02 generating combustion gases having a substantially completeabsence of oxygen, cooling the hot gases to a temperature or from about1500 F. to about 2500 F., admixing dry hydrocarbon vapors with thecooled gases to form a reactant at cracking temperature, soaking thereactant at substantially the mixing temperature for from about one toabout three seconds to form lower molecular weight hydrocarbonsincluding normally gaseous, unsaturated hydrocarbons, cooling thereactant to a lower and polymerizing temperature of from about 1050 F.to about 1800 F., maintaining the reactant at the lower temperature forirom about one to about twelve seconds to polymerize said normallygaseous, unsaturated hydrocarbons to normally liquid aromatichydrocarbons, quenching the reactant to a temperature below 700 F. andrecovering liquid aromatic hydrocarbons from the quenched reactant.

5. A process for thermally treating petroleum hydrocarbons including thesteps of generating combustion gases having a substantially complete:

absence of oxygen, cooling the hot gases to a temperature of from about1800 F. to about 2000 F., admixing dry hydrocarbon vapors with thecooled gases to form a reactant at cracking temperature, maintaining thereactant at substantially the mixing temperature for from about one toabout three seconds to form lower molecu-.

lar weight hydrocarbons, including normally gaseous, unsaturatedhydrocarbons, cooling the reactant to a lower temperature of from about1200 F. to about 1800 F., polymerizing the reactant at lower temperaturefor from about one to about twelve seconds to form normally liquidaromatic hydrocarbons from said normally gaseous,

unsaturated hydrocarbons, quenching the reactant to a temperature below700 F. to substantially terminate further reaction and recovering liquidaromatic hydrocarbons from the quenched reactant.

6. A process for thermally treating petroleum hydrocarbons including thesteps of generating combustion gases having a substantiallycompleteabsence of oxygen, cooling the hot gases to a temperature of from about1500 F. to about 2500 F., admixing dry hydrocarbon vapors with thecooled gases to form a reactant at cracking temperature, maintaining thereactant at substantially the mixing temperature for from about one toabout three seconds to form lower boiling hydrocarbons includingnormally gaseous, unsaturated hydrocarbons, cooling the reactant to alower temperature of from about 1050 F. to about 1800 F., maintainingthe reactant at the lower temperature for from about one to about twelveseconds to polymerize said normally gaseous unsaturated hydrocarbons tonormally liquid aromatic hydrocarbons, quenching the reactant to atemperature below 700 F. and cooling the quenched reactant andseparating therefrom a light condensate comprising mainly normallyliquid hydrocarbons of gasoline boiling range and a heavy condensatecomprising mainly hydrocarbons boiling above the gasoline boiling range,fractionating the condensates to obtain a plurality of successivelyhigher boiling hydrocarbon 1 fractions, recovering from one or saidfractions desired liquid aromatic hydrocarbons, vaporizing another ofsaid fractions and admixing the vapors formed with said first mentionedcooled gases as dry hydrocarbon vapors.

MAURICE B. COOKE.

